Aspects of immune regulation will be studied with special reference to immunologic and genetic mechanisms of control of immunoglobulin and complement component production and catabolism. 4 specific lines of study will be utilized: 1) Mechanisms of antibody mediated immunoglobulin allotype suppression. 2) Mechanisms of antibody mediated complement component suppression. 3) Relationship of H-2 complex to complement component levels in mice. 4) Relationship of humoral substances controlled by the H-2 complex to immunogenicity of heterologous serum proteins.